Boron crystals bombarded by alpha particles release a stream of neutrons with high energy.

This kind of thing was put into the magnetic field by Bot and walked around, and found that there would be no deflection in the magnetic field environment, and the forward path still maintained a straight line.

Therefore, the neutrons were mistaken by Bot for high-energy gamma particles, because they were the only electrically neutral particles that physicists at the time could determine.

As for the kind of electrically neutral particle in the nucleus that Rutherford, the director of the Cavendish laboratory, had always envisioned, Bot didn't take it to heart at all, and didn't think that they said it was a so-called neutron.

After all, this only existed in the imagination of the British, and until he discovered it, mankind had not found any trace of neutrons.

For the sake of conservatism, we can only preconceive that the stream of particles they bombarded is a common gamma particle in daily life.

Later, the Curies replicated Botte's experiment and got the same experimental phenomenon.

Their experimental equipment was better than Bote's, and they measured more accurately that the energy of this high-energy "gamma particle" was about 50 megaelectron volts, far exceeding the highest value of gamma particles known at that time, a few megaelectron volts.

Then the couple went one step further and used the high-energy "gamma rays" produced by the bombardment of light atomic nuclei with alpha particles to continue attacking paraffin wax and other substances.

Paraffin wax is a hydrocarbon mixture of CH, which is not crystalline, but contains a large number of hydrogen nuclei.

When the paraffin wax is bombarded with this high-energy "gamma ray", a large number of protons are bombarded from the inside, that is, the hydrogen atoms in the paraffin wax are shot out from the inside.

For other substances rich in hydrogen atoms like paraffin, the same effect can be produced after being bombarded with high-energy "gamma particles".

The explanation for this phenomenon is that it is also a similar Compton effect.

The incident high-energy "gamma rays" collide with the electrons in the paraffin, transfer the energy to the electrons, so that they can obtain a high enough kinetic energy, and then bombard the hydrogen nuclei in the graphite in the form of protons.

However, the problem comes again, the energy of the incident high-energy "gamma particle" is at least 50 megaelectron volts, but the energy of the outgoing proton is only 5.7 megaelectron volts.

The gap between the two is almost tenfold or so, an order of magnitude difference.

Existing theories cannot explain this strange phenomenon in any way.

Like Bot, the Curies forcibly made a "reasonable" theoretical explanation for this strange experimental phenomenon that they used the knowledge of current physicists.

Of course, in addition to Bot, the two of them were also interfered with by a physics senior.

This predecessor was none other than Bohr, the pioneer of Nordic physics.

It seems that the more famous physicists are, the more they have an unforgettable "cinnabar mole" in their hearts, the depth of love and the depth of hate.

For Einstein, his cinnabar nevus was "quantum mechanics".

Obviously, other people have no doubt about the correctness of quantum mechanics, and regard it as the magic weapon and the only way to calculate the laws of physics in the microscopic world.

Only a small number of physicists, led by Albert Einstein, have always been obsessed with quantum mechanics, that is, how to deny quantum mechanics and what means to prove that quantum mechanics is incomplete and is an erroneous theory.

For Bohr, his cinnabar mole is the "law of conservation of energy".

Since Chadwick measured that the electrons produced by the nucleus in the process of beta decay have a continuous spectrum, which contradicts the prediction of the conservation of energy and momentum during the decay of the two-body body, Bohr questioned the two unbreakable laws of physics in classical physics, the conservation of energy and the conservation of momentum.

Later, Bohr and his assistant Kramers, as well as Slater, a college student visiting Copenhagen from the United States, jointly published a paper entitled "The Quantum Theory of Radiation", in which a theory was proposed, which was later named after the initials of the surnames of the three of them, called the BKS theory, in short, that energy and momentum do not need to be conserved during the microscopic interaction of individual particles, but only need to be conserved at the macroscopic statistical level.

Later, Compton of the University of Chicago in the United States used the conservation of energy and momentum to explain the phenomenon of gamma ray scattering, but at the same time, the analogy should be used to use Einstein's light quantum, that is, yellow's particle theory.

In order to oppose this theory, Bohr, who insisted that light was a particle, revisited the old story and mentioned the BKS theory that the central idea is that energy and momentum are not conserved, which temporarily comforted many physicists who were panicked by their insistence on the wave theory.

Later, however, Compton used his photographs of the cloud chamber to record the trajectories of recoil electrons and scattered gamma rays unmistakably, proving the conservation of energy and momentum at the microscopic level, and completely refuting Bohr and his BKS theory with an irrefutable experimental phenomenon.

Although the Compton Effect experienced a painful failure in academic research, this event did not convince Bohr, and the idea that energy and momentum are not conserved was not completely extinguished in Bohr's heart, but still retained a faint fire.

Later, when this flame met the firewood that could make it burn again, someone made a more accurate measurement of the energy spectrum of beta decay, and the experimental results of this measurement once again confirmed one thing, that is, the beta decay energy spectrum of the atomic nucleus is not the discrete spectrum expected by the theoretical group, but a continuum of gradual decay.

Discrete spectra are based on two assumptions, one is that beta decay will release a lighter nucleus and one electron, and the other is the conservation of energy and momentum before and after the reaction.

Therefore, in order to explain the continuous energy spectrum observed in the experiment, one of these assumptions must be abandoned.

After this experiment was made, Bohr's heart was revived, and he once again carried the big problem of "energy and momentum are not conserved".

In the years that followed, Bohr gave lectures everywhere reminding physicists that the law of conservation of energy does not necessarily apply to a single reaction process that presses atoms.

Bohr was then slapped in the face again, this time by one of his students, Pauli, who had always been known for his sharp language and love of sarcasm.

Bohr wrote a letter to his good student Pauli, in which he explained his repetition of his old ideas, and believed that if it was confirmed that energy was not conserved, it would explain why the sun, which was still an unsolved mystery at the time.

Pauli was uncharacteristically in his reply to Bohr, and in the face of his former teacher, he did not speak sarcastically as usual, but calmly said that Bohr's theory was incorrect, and only proved it one by one at the theoretical level.

Later, Pauli himself came up with a new hypothesis, based on the rejection of the first hypothesis.

He believed that in the process of beta decay, in addition to releasing an electron and a lighter nucleus, a new particle with zero rest mass and electrically neutral and photon will also be released, which will take away a part of the energy, so there is an energy loss.

But because the interaction between this new particle and other substances is so weak, it is difficult for instruments in the laboratory to detect it.

The sum of the energy of the new particle, electron and recoil nucleus is still a fixed value, so in beta decay, the law of conservation of energy still holds, but because the proportion of energy obtained by the new particle and electron can flexibly change with each other, the energy spectral lines of the electron produced by beta decay are continuous rather than discrete.

Because it is a particle in the center of electricity, Pauli named this unknown new particle "neutron" for the time being.

After Chadwick's discovery of the neutron, Pauli's "neutron" was renamed by Fermi, and its future name was finally determined - neutrino.

By 1956, when the neutrinos predicted by Pauli and Fermi were used in the reverse beta decay process in a nuclear reactor, Bohr's artificial hypothesis that energy and momentum are not conserved was finally proved wrong, a small stain on the great physicist's academic career.

When the Curies used the "beryllium rays" produced by the bombardment of beryllium by alpha particles to continue to bombard graphite and produce protons whose energies did not match the theoretical values, they also thought of the hypothesis that Bohr, the giant of Nordic physics, had put forward the hypothesis that energy and momentum may not be conserved at the microscopic level.

Although experiments with the Compton effect confirmed that in his experiments with gamma ray scattering, energy and momentum are conserved.

But this does not mean that energy and momentum are still conserved in other microscopic physical processes, and perhaps they found a counterexample in the "beryllium ray" experiment.

The Curies inherited Bohr's theory, believing that the energy of the high-energy "gamma rays" they measured was only an average, and that when they bombarded a beryllium metal target with alpha particles, there might be higher energy "gamma rays" in the rays.

In other words, at the macroscopic level, energy is conserved, but in microscopic collision reactions of individual particles with individual particles, energy is not conserved.

This hypothesis is a good explanation for why there is a large energy difference between the high-energy beryllium gamma rays and the outgoing protons.

So sometimes, these physicists are really strange, whether it is Bohr or Curie Jr., they are not willing to come up with an unknown new particle that can satisfy the experimental phenomenon, but always think that the existing theory is wrong and think about how to modify it.

Chen Muwu stayed in the Cavendish laboratory during the summer vacation, and recreated it alone, or for the first time, carried out this experiment to discover neutrons, which was basically a repeat of the experiment designed by the Curies Jr.

The experimental setup starts with a polonium-210 source that emits alpha particles, which are collimated and velocity-selective, and then bombarded with boron crystals through an accelerating electric field, so that high-energy "gamma rays", or neutrons, can be produced, as Bott and Curie Jr. call them.

However, because neutrons are electrically neutral particles that are not charged, the method of testing neutrons can no longer use cloud chambers that can record the trajectory of particles through ionized water mist, and other methods must be considered.

The best and easiest way to do this is to use the bombarded neutrons to continue to bombard the paraffin, as the Curies did, and then let the further bombarded protons enter the cloud chamber with a magnetic field.

As long as it can be judged from the trajectory calculation of the cloud chamber that the particles bombarded by the second bombardment are protons, then it can be inferred that the boron crystal was bombarded with alpha particles at the beginning, and the neutrons that came out were indeed born.

If you are not at ease, you can also calculate the energy of the bombarded protons, and you can basically be sure.

Chen Muwu only needs to confirm in the laboratory that he has bombarded the neutrons, and then everything will be fine.

This is equivalent to already holding a big killing weapon in his hand, and all that remains is the question of when he will be made public.

Will it be at the upcoming Solvay conference this year, or will it be when your own school in Sweden will open next year?

Or even if it does, it's still pretending not to know about it.

When you are with Rutherford and the Curie, you can reproduce the experiment and rediscover the neutron in front of everyone.

Of course, in any case, Chen Muwu must now make this experiment himself.

He only knew the general steps of the experiment, specifically, how much to adjust the acceleration electric field, and how thick the target of the boron crystal was cut, and how thick the paraffin target was cut, all of which required a little bit of exploration to come to him.

After a lapse of several months, Chen Muwu finally worked hard again in the Cavendish laboratory and started the experiment diligently alone.

But if he wants to be alone and not be disturbed, it doesn't mean that he can really get what he wants.

Although the original assistants went abroad and returned to China, Chen Muwu's deputy in the laboratory Chadwick also took his wife and children back to his hometown for vacation.

But that doesn't mean no one is free to enter and leave the private lab of the acting director of the Cavendish Laboratories.

"Chen, what are you doing mysteriously hiding here all day? I'm getting married soon, and you're not going to help? Could it be that you are hiding? ”

Kapitsa slammed open the door to the lab.

(End of chapter)